Flow diagram of subjects’ selection.

A total of 4668 employees underwent health screening in 2012, of which 2149 subjects were excluded due to following reasons: absence of ultrasonography or blood biochemical examination; with heavy drinking (daily alcohol intake of 140 g/week or more); with a positive serologic marker for hepatitis B or C; diagnosed with fatty liver based on ultrasonography; taking hypouricemic, antihypertensive, antidiabetic and lipid lowering medication. Consequently, 2383 subjects were observed for incident NAFLD after 4 years.